Many different types of valves are used to control the flow of fluids through a pipe. Usually, some kind of actuator or control is used to regulate the opening and closing of such valves. In many, if not most cases, the actuator will cause rotation of the valve shaft or stem, thereby effecting the valve's opening or closing. In some instances, it is desirable to restrict valve motion by locking it in its open or closed position. Reasons therefore may include the need for system maintenance, repair, or performance testing. Additionally, it may be desirable to test a valve's operability, such as in circumstances wherein a valve is called upon to function only rarely. An example may be in the case of emergency shut down valves (ESV). Applicant's device was designed to accomplish both of these goals, i.e., to permit locking a valve in its open and/or its closed position and to test the operability of an associated valve.